With the progress in computer graphics technology in recent years, data processing devices such as video game machines and simulation machines have become commonly used. A video game machine, for example, is provided with peripherals, such as game pads, joysticks, a monitor, or the like, and a game main unit containing a CPU which implements image processing, sound processing, data communications with the peripherals, and the like. Image processing in video game machines is extremely important in terms of raising the value of the product, and therefore technology for reproduction of animated images has also become highly advanced in recent years. For example, games involving stereoscopic three-dimensional (3D) image representations, rather than two-dimensional images, have come to be widely played, and highly advanced image processing is conducted in games of this kind.
In cases where graphics for game screens are created by means of 3D calculation in order to display three-dimensional images, the representation of images of the game field or player's characters located therein depends greatly or which viewpoint the three-dimensionally created objects are to be observed from. For example, if the viewpoint is set directly to the side of a character, then in the terms of the 3D game, this will produce a "side view", and if the viewpoint is set to directly above a character, then this will correspond to a "top view".
Since the display device used in a video game is a two-dimensional cathode ray tube, it is inevitably difficult to perceive distances in the front-back direction with respect to the screen. Therefore, it a common technique to set a viewpoint such that, of the three-dimensional coordinate axes, X, Y and Z, a coordinate axis wherein detailed perception of distance is not required in relation to the contents of the game is set in the front-back direction, namely, perpendicular to the front plane.
For example, in a 3D shooting game, as shown in FIG. 14, enemies and missiles approach from in front and the player's craft has to avoid these enemies and missiles by moving up and down, and left and right. In this case, the player moves in the up and down direction and left and right direction and these directions are therefore very important. On the other hand, the front-back distance is of little relative importance. Therefore, in a 3D shooting game of this kind, the two-dimensional screen is set in the up-down and left-right planes, whilst the front-back plane is set perpendicular to thin.
In this way, in a 3D shooting game it is not especially an impediment if the line of sight is fixed in a forward direction, but there exist other types of game. For instance, in a game where the player controls a character to fight with opponents, or in a game where the character has to break through various obstacles, there are cases where the coordinate axis in which a detailed perception of distance is required may change depending on the shape of the landscape in which the character operated by the player is moving, or the player's own preferences or skill level. In other words, it is not possible to create an appropriate playing environment using only a single type of viewpoint.
Technology corresponding to this is represented by a "virtual button". This is a device whereby a desired viewpoint is continually selected from a plurality of prepared types of viewpoint, in accordance with the player's individual preferences.
However, using a "virtual button" has a disadvantage in that it adds an "operation for changing the viewpoint" to the original game operation, and therefore makes the game operation more complex. Furthermore, since the player has to look for the optimum viewpoint him or herself, it obstructs his or her concentration on playing the game.
This invention was devised in order to overcome problems of this kind, an object thereof being to provide an image processing device whereby an optimum viewpoint is automatically provided, thus creating a favourable game environment, without burdening the player, and a game machine using this image processing device, an image processing method and a medium whereon programs for same axe recorded.